Single-primary Mode DR proxy sync

General
1

In a setup with a Single-primary Mode, having HA pair and a DR node.
The DR node would be connected to both Primary and Secondary nodes, however what are its rules on Sync’ing, should it only sync from the primary node, or does it sync from both primary and secondary HA pair.

2

All replication will originate from the Primary node and be pushed out to all secondary nodes. After all, you can only write to the primary. So, all new data will originate there.

If you’re perhaps referring to re-syncs after a disconnect, any node with good “UpToDate” data could be the “SyncSource”. There will only be one SyncSource though, it won’t get half the updates from one node and other half from another. In most circumstances, the Primary node is likely to be chosen as the SyncSource.

3

Thanks for your response.
is there a configuration for SyncSource, or is it just a native part of the application, that it should sync from the Active HA Node.

Thanks

4

Deciding SyncSourc and SyncTarget is all handled via internal logic based upon the meta-data and bitmap comparisons that occur on the initial connection. It may not always be the active HA node, but in most circumstances it will be.

There is no way to manually configure how the SyncSource and SyncTarget are decided, but there are ways to trigger full resyncs (full overwrites) of specific peers if desired.

For more information on the internals mechanisms which decide all this see the “Learning More” chapter in the user’s guide: https://linbit.com/drbd-user-guide/drbd-guide-9_0-en/#p-learn

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